Re: [PATCH 2/3] KVM: x86: Save&restore interrupt shadow mask

Gleb Natapov
2010-02-17T09:05:58Z

On Tue, Feb 16, 2010 at 10:06:12PM -1000, Zachary Amsden wrote:
> On 02/16/2010 02:39 PM, Marcelo Tosatti wrote:
> >On Mon, Feb 15, 2010 at 10:45:42AM +0100, Jan Kiszka wrote:
> >>The interrupt shadow created by STI or MOV-SS-like operations is part of
> >>the VCPU state and must be preserved across migration. Transfer it in
> >>the spare padding field of kvm_vcpu_events.interrupt.
>
> STI and MOV-SS interrupt shadow are both treated differently by
> hardware. Any attempt to unify them into a single field is wrong,
> especially so in a hardware virtualization context, where they are
> actually represented by different fields in the undocumented but
> nevertheless extant format that can be inferred from the hardware
> virtualization context used by specific vendors.
>
The problem is SVM doesn't distinguish between those two. But we shouldn't
design out interfaces based on SVM brokenness.

--
Gleb.